alas, no
I got off the phone with Apple Care; I even got passed off to a 'product specialist', and she acknowledged "the older iMac might not fully support the newer keyboard"
She guided me through downloading "KeyboardSoftwareUpdate1.2" and still nothing. It's probably only of benefit once the OS is fully loaded.
The "workaround" is to use the Apple Remote!
Holding its "Menu" button while powering on has the same effect as holding "Option" on a (functioning) keyboard.
Oh well, at least I can to boot to my FireWire drive, which I created with SD.
I guess I'm off to buy the license now...
Thanks again!